The reasons why they go unreported are in much greater magnitude in a place like India where both women and lower caste members of society have less effective rights, justice system doesn't care about rapes, and law enforcement is corrupted into not dealing with them (if the stories that keep flooding reddit are accurate anyway).

So while they do go unreported everywhere, the degree to which they are seems it would be obviously different when you consider how hostile/indifferent one country is toward rape victims than another.